The left atrial appendage is a dead end in the blood flow through the heart, but during systole it is filled with blood. As compared to the right atrial appendage, it is longer, thinner and has more undulating surface. From the medical point of view, this organ does not have any significant role. In the case of atrial fibrillation, the left atrial appendage is insufficiently washed by blood, which results in the congestion of the blood. Congestion may cause activation of the coagulation system and formation of blood clots. Blood clots from the inside of the appendage can be released to the cardiovascular system and transferred to important vital structures. Therefore, a frequent complication of atrial fibrillation is an ischemic stroke of the organ perfused by blood containing clots, in the worst case, a cerebrovascular accident. Atrial fibrillation affects about 1% to 2% of the adult population, and every tenth patient over 80. It increases the risk of stroke by five times, while every fifth stroke is associated with this cardiac arrhythmia. Ischemic strokes associated with atrial fibrillation are more often fatal, and patients who survive are often disabled and more often exposed to repeated episodes than patients after strokes caused by any other reason. As a consequence, the risk of death after a stroke due to atrial fibrillation is doubled, and the cost of treatment is 1.5 times higher.
Known solutions aimed at stopping the blood flow through the lumen of the left atrial appendage can be divided into two groups. The first group of solutions aims at closing the blood supply from the inside. The second group of solutions aims at closing the blood supply from the outside by occluding the appendage using an occlusion device from the outside, at the base of the appendage.
A known solution belonging to the first group of solutions is disclosed in U.S. Pat. No. 6,652,555, expressly incorporated herein by reference. This known solution proposes a number of solutions employing a membrane for blocking passage of clots from the inside of the left atrial appendage to the inside of the left atrium. The membrane, secured inside, over, or around the ostium prevents blood clots from escaping from the appendage to the lumen of the left atrium. The membrane may be designed as permeable or impermeable with respect to blood flow, but in either case, stopping blood clots. The membrane is configured to extend over the ostium of the left atrial appendage; therefore, it has an outer periphery with a larger dimension than a dimension of the ostium. According to some embodiments, securing elements are designed so that the membrane has a central mandrel on which an element with self-expanding arms is inserted to the interior of the appendage, what makes it possible, in the next step, to occlude the ostium of the appendage between the membrane and the arms of the element located from the interior of the appendage, when they have been opened.
In another solution, known from US patent specification No. US 2005/0113861, expressly incorporated herein by reference, a different solution is disclosed. According to this known solution, a device comprises a center post and a sheet, stretched over a plurality of ribs, blocking the outflow of blood clots from the left atrial appendage. The sheet stretches over the ribs like a parachute, where from the interior of the appendage there is an open space left, whereas from the left atrium the flow of blood is closed by the sheet.
Another solution belonging to the first group of solutions, known from US patent specification No. US 2006/0247680, expressly incorporated herein by reference, discloses a method and an implantable flange for occluding the blood orifice from the atrium to an appendage. The flange is secured in the lumen of the left atrial appendage, near the orifice, and contains a bigger plate on the atrium side, with a resistance flange and a second plate secured to the flange on a cylindrical wall from the inside of the left atrial appendage. The flange, both plates and the cylindrical wall are semi-flexible. Both plates can be tightened to each other using a screw mechanism, causing the cylindrical wall to bulge radially outward and the flange to be fixed in the orifice of the left atrial appendage.
Another solution belonging to the first group of solutions, known from U.S. Pat. No. 8,828,051, expressly incorporated herein by reference, discloses another device for occluding the interior of the left atrial appendage. The occlusion device comprises a kind of an occluder in the form of a disk configured to prevent blood flow to the left atrial appendage. The occluder, according to this known solution, comprises a main flange, blocking blood supply to the appendage from the left atrium and an auxiliary anchoring flange connected thereto via a flexible connector. The auxiliary flange inserted into the appendage opens up, preventing the whole from prolapsing into the atrium. Coils of the flexible connector are connected with the occluder disk, where the connector has a substantially constant cross-section and allows for variable length, variable orientation, as well as it being bent according to the appendage position. The anchoring flange is inserted in a coiled configuration into the atrium and it contains a shaped edge in the form of an umbrella, preventing prolapsing from the left atrial appendage.
As their design indicates, devices belonging to the first group of solutions need to be arranged in the ostium of the left atrial appendage only from the interior of the left atrium.
Solutions belonging to the second group are external occlusion devices placed at the base of left atrial appendage, without surgical intervention providing access to the inside of the heart. This is usually performed during a surgery by applying an occlusion device on the appendage stalk, which constricts and occludes internal surface of the orifice. This type of an occlusion device must meet stringent requirements. In addition to material requirements as to interaction with body fluids, the pressure force of arms must be constant and must be within strictly defined limits.
Too weak pressure of arms may not be able to stop blood flow to a left atrial appendage and blood outflow from a left atrial appendage. Limiting blood flow only by a partial occlusion of the flow may cause increased formation of blood clots, which may lead to an increased risk of a stroke.
However, too strong pressure of the occlusion device arms may cause necrosis. This means that the pressure force of arms must be within strictly defined limits.
A known solution belonging to the second group is disclosed in the patent specification of international application No. WO 2009/106907, expressly incorporated herein by reference. This specification discloses a left atrial appendage closure device to be placed external to the appendage. The device, according to this known solution, comprises an annular elastic band for medical applications, particularly made of medical silicone or a polymer containing medical silicone. First, the band is enlarged, and after positioning the enlarged band from the outside at the base of the appendage, the elastic band is released from enlarging surgical forceps. When released from the forceps, the band returns to its original size, tightening the base of the appendage causing the closure thereof. In another embodiment of the solution according to this known invention, the described device comprises an additional elastic element associated to the annular elastic band, for example a coil spring, or a mesh, made of biocompatible metal alloy.
Another solution, known from the patent specification of US Patent Application No. US 2004/0030335, expressly incorporated herein by reference, discloses a device and method of use for occluding animal or human tissues. According to this known solution, a clamping ring is disposed on the left atrial appendage. In the first stage, a cover fixed at the end of an arm of a device supplying a gas medium is placed on the appendage from the outside. The clamping ring for clamping the appendage at the base is fixed on the cover. After placing the cover on the appendage, the clamping ring is slid off the left atrial appendage, and the cover is filled with air, which reduces the volume of the appendage, which facilitates clamping of the clamping ring and facilitates removal of the cover from the appendage.
A further known solution from the second group is disclosed in U.S. Pat. No. 8,647,367, expressly incorporated herein by reference, which discloses devices, systems and methods for occlusion of the left atrial appendage. According to this known solution, in the first stage a concentric tube of the device is inserted from the left atrium, wherein an outer jacket allows the inflation of a balloon sealing off blood flow to the appendage, whereas an inner tube is used to aspirate the interior of the appendage. After performing these steps, an outer closure device in the form of a loop is placed at the basis of the appendage.
A different known device belonging to the second group of solutions has been in use. It has the form of an elastic element made of titanium alloy wire with a shape memory, cooperating with a body composed of titanium tubes lined with polyurethane foam lining, wherein the whole is trimmed with polyester knitted fabric. The position of a frame of the device kept in a stretched position by means of threads is rearranged to perpendicular after putting the device through a cannula between ribs. Then, the device is placed on a left atrial appendage, and the threads releasing a spring are cut off, leading to the occlusion of the lumen by the spring, at the base of the left atrial appendage.
However, in most of the solutions belonging to the second group, where surgical intervention inside the heart is not required, it is necessary to lead the entire length of an appendage through the device and only then it is possible to place an occlusion device at the base of the appendage.
Another known solution is disclosed in US patent specification No. US 2008/0039879. This known solution discloses a number of embodiments of an occlusion device, including several variants of clips and springs occluded on an appendage.